Systems have been in use in the past for programmable, automated assembly of electronic components to substrates. Commonly, automated programmable machines for effecting such assembly are referred to as “Pick and Place” machines. Such substrates include, but are not limited to, rigid substrates such as printed circuit boards (PCBs) or the like. Unless indicated otherwise, the term “PCB” will be used hereinafter to refer not only to conventional printed circuit boards, but also inclusive of all other substrates that may be used with Pick and Place machines, including for example, flex cables. Such electronic components to be assembled to the substrates may include microprocessors, integrated circuits, transistors, resistors, connectors or the like.
Frequently, it is necessary to operatively connect multiple Pick and Place machines in series that form a “line” to achieve desired levels of productivity and throughput, or accommodate highly complex PCBs or PCBs with larger numbers of components to be placed. In such a case, certain of the Pick and Place machines in a line will be dedicated to placing certain of the components on the PCB. If one of the Pick and Place machines in the line is inoperative for any reason, it generally is possible for PCBs to be passed through the inoperative machine to other operative machines in the line.
For instance, the HS50 and S23 brand Pick and Place machines from Siemens GmbH of Munich, Germany includes a vertical elevator at each end of a Pick and Place machine with a conveyor extending beneath the machine from the front vertical elevator to the back vertical elevator. In this manner, a particular PCB could bypass the machine by just being conveyed therethrough; such as if the PCB is defective or the machine is inoperative. Alternatively, PCBs could bypass the particular machine by using the vertical elevators and the conveyor underneath the machine if the machine itself is inoperative. However, this approach is relatively slow and cumbersome and not adapted to frequent use in high volume production lines. Moreover, even with such a bypass mechanism, it may be difficult to complete the assembly of all of the components to a particular PCB in one pass. The overall productivity of the serial Pick and Place machines is thus reduced or limited.
In an effort to enhance the productivity of Pick and Place machines, and to conserve on floor space, Pick and Place machines have been produced that include two parallel internal conveyors and two independent Pick and Place mechanism for simultaneously processing two PCBs in parallel on each of the conveyors within a particular machine. Generally, the output from each independent Pick and Place mechanism within a machine is then transported by a separate conveyor to the next machine in the line. However, even with this arrangement, if one of the Pick and Place machines in a line is inoperative, the effectiveness of the entire line is severely impacted.
Therefore, conventional systems for assembling electronic components to printed circuit boards, while having their own utility, may not be entirely satisfactory in terms of redundancy and flexibility, if one or more of the electronic assembly module are inoperative.